reiserfs: remove obsolete __constant_cpu_to_le32

__constant_cpu_to_le32 converted to cpu_to_le32

Cc: reiserfs-devel@vger.kernel.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>